The invention resides in venting arrangement for a crankcase of an internal combustion engine including a centrifugal oil separator with a housing having an inlet passage for the admission of an oil-air mixture and an outlet opening for the discharge of purified air.
Such a venting arrangement is known for example from DE 196 07 919 A1, wherein the oil particles in the oil-air mixture of an engine crankshaft are removed from the mixture and are returned to the crankcase. The venting arrangement includes a centrifugal oil separator with a rotating housing which has several radial inlet passages which lead to a central axially extending exit channel. The oil air mixture is conducted radially from the outside to the inside by way of the inlet passages in which baffles are arranged. Because o:f the centrifugal forces generated by the rotation of the housing, the oil particles of the oil-air mixture are deposited on the baffles and move radially outwardly against the in-flowing oil-air mixture. The air from which the oil particles have been removed exits by way of a discharge conduit and is supplied to the air intake duct of the engine.
This venting arrangement has the disadvantage that, on one hand, the oil air mixture is conducted from the outside radially inwardly and, on the other hand, the oil particles deposited are directed again outwardly against the inward flow of the air-oil mixture so that two opposed flows are formed in the inlet channel. This results in a limited efficiency of the venting arrangement with regard to flow volume as well as the separation effectiveness. The opposite flows inhibit each other and cause re-entrainment of oil particles in the air. Also, an increase in the speed of the centrifugal separator will not lead to an improved efficiency since, with increasing rotational speed, the outwardly flowing oil increasingly carries along the inwardly directed air-oil mixture flow.
It is further disadvantageous that a certain minimum excess pressure must be established in the housing interior to provide for the inward flow of the oil-air mixture. Also, this inwardly directed flow detrimentally affects the purification degree since oil particles which had been deposited but are again thrown outwardly by the centrifugal forces are re-entrained in the oil-air flow and are again carried into the interior of the housing.
It is the object of the present invention to improve the efficiency of a venting arrangement including a centrifugal oil separator by simple means.